AutoVE troubles

[DrX]

I have been trying to tune for the new larger TB and trans using AutoVE. Worked better before I did any logging and AutoVE adjustments. Now every BEN map log shows way lean at around the 155 kPA/3600-4000 RPM cells. Just bogs and the AFR shoots up if I hit the throttle when I'm rolling at a decent speed. Injector duty cycle is usually in the 30% range during this. Fuel pressure is great with the new fuel system. AutoVE paste and multiply adjustments just give me a larger and larger spike in the boost VE table but it has no effect on AFR after reflashing. After multiple logs and reflashes the BEN map still looks like this. Did I mess up or is something strange going on here?

[TAQuickness]

how many samples do you have at 155/3000? Looking at your map, you don't have any filters or low cell counts applied. It could be a throttle transient giving you a bum reading. I would also check for exhuast leaks around the WB.

[Doc]

TA beat me to it with the number of counts and filtration. Also, that part of the map usually takes more time for me to get a good number of samples on the public road. A load bearing dyno would be quicker, safer but I know-more money.

[DrX]

This was just a quick test log and I am using it for illustration purposes only. But they all look pretty much the same. I always use the filter before applying VE corrections. This does happen as soon as I hit the throttle though. Cant even get past this point anymore. It should be going pig rich with the numbers that are in the Boost VE table now. At higher and lower boost levels commanded and wideband AFRs are very close.

Saw some crazy boost numbers(12-13psi @ -16*C ambient) on 1 of my first logging runs to 6000 RPM. But it never went lean. Did have some issues with it stalling when shifting into gear from Park after the reflash. Mostly when cold. Rolling back the tune didn't help. Not sure if it was the tune or some other issue but it is better now(idle relearn??). Idle in Park is very smooth and idle vacuum is 17-18 on the gauge.

Seems great at lower loads. A part throttle kickdown into 1st at 50 KMH breaks the tires loose.

Going to try rolling back the Boost VE table to something more reasonable and see what happens. Will check for leaks.

[joecar]

Is your IFR table correct...?
Is your fuel pressure regulator vacuum referenced...?

[DrX]

Thanks guys.

Think I got it figured out. We'll see.

I think the idle issue was just that the PCM had already done a little learning which was lost when I reflashed. Once/if I get the idle parameters setup properly for the new TB that shouldn't happen.

As you suggested, the low cell count filter wasn't doing anything. Looks like I had changed the "considered empty" value to "0" last time I did some logging a few months back.

I just adjusted the BoostVE table back down to more sensible values and went for a non-logging drive. Didn't see any lean outs on the AFR gauge. It was rich everywhere in boost.

IFR table is flat(5g/s) and FPR is boost-referenced.

[DrX]

Did a few logs and used AutoVE to tweak the VE table slightly. Altered the BoostVE table manually. It's coming along nicely. Pretty steady around 11.8 AFR now in boost which is what I have commanded. Highest I hit on the logs was around 5500 RPM/9.5 psi boost. Still looks like the injectors will be at 100% by 6000 RPM even with the FP well over 70 psi.

[joecar]

What is your injectors' rated flowrate/pressure...?

What is your fuel rail pressure with the vacuum/boost hose disconnected...?

[DrX]

What is your injectors' rated flowrate/pressure...?

What is your fuel rail pressure with the vacuum/boost hose disconnected...?

I have the "42lb"(36lb @ 43.5psi) injectors that came with the Radix kit. Whoa, I have the base pressure at the rail cranked way up to 70psi right now! Turned it up some more last week without pulling the vac line off(don't know where my mind was)! That makes the injectors 45.7lbers(5.76g/s). Although I don't think the 5g/s in the original Mag tune equates to 42lb/hr either. More like 5.3g/s isn't it? Obviously I have compensated with the VE table. My duty cycle was something like 86% @ 5400 RPM at the current pressure. So it will be much higher if I drop the pressure back down to 60psi. Correct?

[joecar]

When you measured 70 psi with the vac line still on, what manifold absolute pressure (MAP) does it run...?

For MAP referenced FPR's:

flowrate = sqrt((FP + BARO)/RatedPressure) x RatedFlowrate

(using consistent units, first convert lb/hr to g/s, and psi to kPa)

When you pull the vac line off, the FPR puts out FP + BARO (measured at fuel rail).

If vac line was still on, the FPR puts out FP + MAP (measured at fuel rail), which allows FP to be determined and used in the above calc.

If it were possible to have MAP equal to 0 (!!!), then FPR would put out FP (as would be measured at fuel rail).

Note: FP + BARO comes from the pressure difference across the injector: (FP + BARO + MAP) - MAP
where FP + BARO is the absolute base pressure of the FPR.

Edit: added more info.

[DrX]

When you measured 70 psi with the vac line still on, what manifold absolute pressure (MAP) does it run...?

For MAP referenced FPR's:

flowrate = sqrt((FP + BARO)/RatedPressure) x RatedFlowrate

(using consistent units, first convert lb/hr to g/s)

When you pull the vac line off, the FPR puts out FP + BARO (measured at fuel rail).

If vac line was still on, the FPR puts out FP + MAP (measured at fuel rail), which allows FP to be determined and used in the above calc.

If it were possible to have MAP equal to 0 (!!!), then FPR would put out FP (as would be measured at fuel rail).

Note: FP + BARO comes from the pressure difference across the injector: (FP + BARO+ MAP) - MAP.

Actually, it was 70 with the vac line off, 60 with it on. So the FPR was cutting back about 10 psi to compensate for idle vacuum. From my logs it looks like idle kPa was around 40(vac line on). (105-40) kPa/6.897 kPa/psi= 9.4 psi

I can tidy up(increase) the IFR and VE tables but it won't help my Inj Duty Cycles. Particularly if I want to lower the FP somewhat. Looks like I still need some larger injectors to be safe.

edited to add detail

[joecar]

Actually, it was 70 with the vac line off...
Then FP+BARO = 70 psi

This is the pressure difference across each injector
(the MAP referenced FPR adjusts fuel pressure such that there will be a constant pressure difference across any injector under all MAP conditions (vac or boost):
(FP +BARO + MAP) - (MAP)).

(The rated pressure is the pressure difference during rating since the injector is in the atmosphere (i.e. no vacuum)); the quoted pressure is 'gauge pressure' which is relative to BARO, so must add BARO to it to convert it to absolute pressure (must work in absolutes since MAP is absolute):
(RatedPressure + BARO) - (BARO) = RatedPressure

The flow rate depends on the squareroot of the pressure difference.

Okay, just doing the math to see what happens...

flowrate (flatline) = sqrt((FP+BARO)/RatedPressure) x RatedFlowrate
= sqrt(70 psi/43.5 psi) x 36 lb/hr
= 45.7 lb/hr
= 45.7 lb/hr x 453.6 g/lb / 3600 s/hr
= 5.76 g/s

This is 15% bigger than the 5 g/s which your VE is tuned to;
I can't really say if this makes any difference... :nixweiss:
I do hope I crunched the numbers correctly...:banana:

Note: for non-referenced FPR, the formula is slightly different:

flowrate (sloped) = sqrt((FP + BARO - MAP)/RatedPressure) x RatedFlowrate

I could be all wet, but I'll never find out otherwise...:muahaha:

[DrX]

I do hope I crunched the numbers correctly...:banana:


I got this same result(5.76g/s). Of course it's irrelevant if I change the FP or injectors! Pump output drops off too much as FP rises. I need a happy balance between FP and IFR that yields acceptable Inj Duty Cycles.